Alexander H. Kortsaris

Protein tyrosine kinase inhibitor, genistein, enhances apoptosis and cell cycle arrest in K562 cells treated with γ-irradiation

Genistein, is a natural isoflavone compound with a potent activity against protein tyrosine kinases. The leukemic cell line, K562, is a bcr/abl (Philadelphia chromosome) positive cell line that is resistant to DNA-damaging agents, including γ-irradiation. Treatment with genistein increased apoptosis and promoted G2-phase arrest in the non-apoptotic population of the γ-irradiated K562 cells. Irradiated cells that survived 72 h after the irradiation had a normal distribution in cell cycle, whilst genistein treatment kept cells arrested in the G2-phase, decreased the S-phase fraction and suppressed DNA-synthesis. Taken together, our results show that genistein augments apoptotic cell death after γ-irradiation in K562 cells and this result cannot be attributed to abrogation of the G2/M checkpoint.

Antiproliferative Effect of Mineral Trioxide Aggregate, Zinc Oxide-Eugenol Cement, and Glass-Ionomer Cement Against Three Fibroblastic Cell Lines

An important requirement for dental materials placed in direct contact with living tissues is biocompatibility. The purpose of this study was to evaluate the antiproliferative activity of three dental materials (mineral trioxide aggregate, zinc oxide-eugenol cement, and glass-ionomer cement) against a panel of established fibroblastic cell lines (L929, BHK21/C13, and RPC-C2A). The materials were prepared according to the manufacturers instructions and were tested in insert wells for 12, 24, and 48 h. Cell number fraction was estimated by the sulforhodamine-B assay, in reference to controls. The degree of antiproliferative effect in ascending order was mineral trioxide aggregate, glass-ionomer cement, and zinc oxide-eugenol cement in all cell lines tested.

Effects of melatonin on proliferation of cancer cell lines

Papazisis KT, Kouretas D, Geromichalos GD, Sivridis E, Tsekreli OK, Dimitriadis KA, Kortsaris A.H. Effects of melatonin on proliferation of cancer cell lines. J. Pineal Res. 1998; 25:211–218.

In vitro cytotoxicity of six dentin bonding agents.

The cytotoxicity of six dentin bonding agents (Syntac, Solobond, Bond 1, Scotchbond 1, Heliobond and F-2000) was tested against an established cell line, L929. Under aseptic conditions 3, 5 and 10 microL dentin bonding agents were placed in the centre of Petri dishes. Each dish was covered with a 5-mL suspension of fibroblasts at a concentration of 40 000 cells mL(-1). The cultures were incubated at 37 degrees C and cytotoxicity was assessed by a quantitative technique at 24 and 72 h. All the dentin bonding agents were found to be cytotoxic. Scotchbond 1 and F-2000 showed the highest cytotoxicity followed by Solobond and Bond 1. Heliobond and Syntac were the least toxic materials.

Cytotoxic effects of different concentrations of neutral and alkaline EDTA solutions used as root canal irrigants

The cytotoxic effects of neutral and alkaline EDTA solutions were evaluated and compared with those of sodium hypochlorite solution using an established cell line: L929. Cytotoxicity was assessed by a quantitative technique at five observation periods (1, 3, 6, 12, and 24 h). All tested agents showed moderate to severe cytotoxicity in the present experimental model in a concentration-dependent manner.

In vitro release of hydroxyl ions from calcium hydroxide gutta-percha points.

In endodontic practice, calcium hydroxide is widely used for a number of reasons associated with its high pH. The purpose of the present study was to determine in vitro the alkalizing potential of newly introduced calcium hydroxide gutta-percha points that are proposed for temporary filling of root canals. The materials tested were: calcium hydroxide gutta-percha points; chemical pure calcium hydroxide powder mixed with distilled water; and Reogan rapid, a nonsetting calcium hydroxide preparation. The materials were placed into dialysis tubing and transferred into plastic vials containing bidistilled water. Measurements were taken by a digital pH meter after 10, 20, and 30 s; 1, 15, and 30 min; and 1, 2, 3, 24, 48, 72, 96, and 120 h. The calcium hydroxide containing gutta-percha points showed a significantly lower alkalizing potential than Reogan rapid and calcium hydroxide mixed with distilled water (p < 0.05).

In vitro release of hydroxyl ions from six types of calcium hydroxide nonsetting pastes

The role of intracanal medication in root canal treatment is very important. Calcium hydroxide (Ca(OH)2) is considered to fulfill many of the properties of an ideal root canal dressing mainly due to its alkalizing pH. It is bacteriocidal and neutralizing to the remaining tissue debris in the root canal(s) and through the continuous release of OH- ions it promotes an alkalizing osteogenic environment for the surrounding tissues. The purpose of this study was to examine the pH values of various Ca(OH)2 based on compounds used as intracanal medicaments over a period of 5 days. The following materials were tested: Calasept, Calcicur, Calxyl blue, Calxyl red, Reogan rapid, and Tempcanal. After a fast OH- release period (2 h) each compound reached an asymptotic pH state. The results showed that all materials exhibited alkalizing pH with Reogan rapid, Calxyl Red, and Calcicur being the most potent (p = 0.05). The final pH of each compound correlated positively with the Ca(OH)2 mass fraction contained in it.

In vitro evaluation of the cytotoxicity of two glass-ionomer root canal sealers.

The cytotoxicity of two glass-ionomer root canal sealers (Ketac-Endo and Endion) was tested by using an established cell line, BHK21/C13. Under aseptic conditions, the sealers were prepared according to the manufacturers directions, and 0.1 ml of each material was placed in petri dishes. After setting for 6 h, the sealers were covered with 20 x 10(4) cells per dish. The cultures were incubated at 37 degrees C for 24 h, 48 h, and 72 h. Cytotoxicity was assessed by a quantitative technique at three observation periods. Endion was highly cytotoxic, causing a significant decrease in cell density. Ketac-Endo proved to be a very biocompatible material.

CDK-inhibitor olomoucine inhibits cell death after exposure of cell lines to cytosine-arabinoside.

Signal transduction for apoptosis or programmed cell death, after DNA damage in mammalian cells, is believed to involve activation of cyclin-dependent kinases (CDKs), especially CDK-1 (cdc2) and CDK-2. We used CDK-inhibitor olomoucine, a purine analogue to evaluate the role CDK inhibition on cytosine-arabinoside (Ara-C)-induced cell death. The two drugs showed an antagonistic effect, suggesting that apoptosis after exposure to Ara-C is inhibited by olomoucine. DNA-electrophoresis showed a clear inhibition of the apoptotic pattern when olomoucine was added to Ara-C. We conclude that CDK-inhibitor olomoucine inhibits cell death induced by Ara-C.